feat(kiro): enhance request translation and fix streaming issues

English:
- Fix <thinking> tag parsing: only parse at response start, avoid misinterpreting discussion text
- Add token counting support using tiktoken for local estimation
- Support top_p parameter in inference config
- Handle max_tokens=-1 as maximum (32000 tokens)
- Add tool_choice and response_format parameter handling via system prompt hints
- Support multiple thinking mode detection formats (Claude API, OpenAI reasoning_effort, AMP/Cursor)
- Shorten MCP tool names exceeding 64 characters
- Fix duplicate [DONE] marker in OpenAI SSE streaming
- Enhance token usage statistics with multiple event format support
- Add code fence markers to constants

中文:
- 修复 <thinking> 标签解析：仅在响应开头解析，避免误解析讨论文本中的标签
- 使用 tiktoken 实现本地 token 计数功能
- 支持 top_p 推理配置参数
- 处理 max_tokens=-1 转换为最大值（32000 tokens）
- 通过系统提示词注入实现 tool_choice 和 response_format 参数支持
- 支持多种思考模式检测格式（Claude API、OpenAI reasoning_effort、AMP/Cursor）
- 截断超过64字符的 MCP 工具名称
- 修复 OpenAI SSE 流中重复的 [DONE] 标记
- 增强 token 使用量统计，支持多种事件格式
- 添加代码围栏标记常量

internal/translator/kiro/openai/kiro_openai.go

@@ -156,8 +156,9 @@ func ConvertKiroStreamToOpenAI(ctx context.Context, model string, originalReques
 		}
 
 	case "message_stop":
-		// Final event - emit [DONE]
-		results = append(results, BuildOpenAISSEDone())
+		// Final event - do NOT emit [DONE] here
+		// The handler layer (openai_handlers.go) will send [DONE] when the stream closes
+		// Emitting [DONE] here would cause duplicate [DONE] markers
 
 	case "ping":
 		// Ping event with usage - optionally emit usage chunk